1. Field of the Invention
The present invention relates to a display device which is so constituted as can be detachably attached to a control device that feeds data to be displayed, and to a casing for containing the display device that is detached.
2. Prior Art
A CRT or a liquid crystal panel has generally been used as a display device for displaying data. In such a display device, the electric power must be maintained supplied together with data to be displayed while the data is being displayed. Modern liquid crystal panels are consuming electric power in very greatly decreased amounts. Though the electric power may be consumed in decreased amounts, the data that is displayed disappears if the power source circuit is broken.
There has further been developed another display device having a memory property. As the display device having a memory property, there have been known, for example, a ferroelectric liquid crystal display and an electrophoretic display. These display devices maintain the displayed data even after the power source circuit is broken once the data has been electrically written by a drive circuit or the like circuit. By utilizing this property, it has been attempted to use the device in a state of not being supplied with electric power by separating the display unit from the power source.
However, the display device having such a memory property involves a problem in that the image that is maintained displayed undergoes a change when the display device that is being separated from the power source receives electric, electromagnetic or magnetic noise from the outer side. Even in a display device without memory property such as CRT, it is considered that the displayed image may undergo a change upon receiving noise. However, the display device without memory property such as CRT, is supplied with data to be displayed and with electric power at all times to rewrite data at all times. Even in case the displayed image instantaneously changes due to noise, the displayed image is restored at a next moment due to the rewriting effected at all times, and the displayed image is not almost affected by a small degree of noise. Therefore, no countermeasure needs to be taken against noise of small degrees.
With the above display device having a memory property, however, if the displayed image undergoes a change due to noise in a state where the display device is separated away from the power source, the display that is changed cannot be returned to the initial display, since the display device is supplied with neither the data being displayed nor the electric power for rewriting the data. Accordingly, the image that is changed upon receiving noise is maintained displayed. Further, the displayed image deteriorates every time when it receives noise. Despite of its memory property, therefore, the display device is not capable of maintaining the displayed image for extended periods of time.
The present invention was accomplished in view of the above-mentioned circumstances, and provides a display device having a memory property which is capable of maintaining the displayed image even in a state where the display device is separated away from the power source as a result of decreasing the effect of external noise.
In the display device of the invention, an input unit that receives data to be displayed and electric power is provided with an input protection unit which is an electric load such as diode, IC, resistor or capacitor, and when a drive IC is provided, the drive IC is used as the input protection unit. Further, the connection terminals that serve as an input unit is provided with a cover having at least the outer surface layer or the inner surface layer made of a material that shields at least the electric field, electromagnetic field or magnetic field in a state where the display device is detached. Further, the outer surface layer of the display device is formed of a material which shields at least electric field, electromagnetic field or magnetic field.
By employing this constitution, there is realized a display device which does not permit the displayed image to be changed as a result of decreasing the external noise despite the display device is separated away from the control unit.
The invention further provides a case for containing a display device having an image display unit with a memory property that continues to display the image even in a state of not being supplied with electric power, wherein at least the outer surface layer or the inner surface layer is formed of a material that shields at least electric field, electromagnetic field or magnetic field. Upon containing the display device in such a case, external noise is prevented from infiltrating into the display device, and an image is maintained displayed on the display device.